Wireless communications devices, such as cellular telephones, have proven very popular. Over time, these devices have been reduce greatly in size and weight. Today, it is common for a cellular phone to have a small main body and a flip cover coupled to the main body via a hinge mechanism. It is desirable for the flip cover to remain in the closed position until the user desires to use the device, when the flip cover is opened, exposing a keypad. In the open position, the device is typically long enough to stretch from a person's mouth to their ear. The user speaks into the flip cover and listens to the opposite end of the main body. Once in the open position, it is desirable for the flip cover to remain open until deliberately closed by the user.
Due to the small size and desire for light weight, plastic parts are typically employed for the hinge mechanisms linking the flip cover and the main body. One common configuration is to use a flip cover that connects to the main body via two coaxial hinges. The first hinge is typically a simple shaft and collar arrangement that performs the dual function of allowing relative rotational motion and provides an acoustic coupling path between the flip cover and the main body. The second hinge is typically a simple shaft and collar arrangement without acoustic coupling characteristics. Further, it is typical for at least one of the hinges to include some sort of detent arrangement so as to hold the flip cover in a predetermined opened position when opened. One type of detent arrangement is through the use of cammed surfaces and lateral force applied through a common coil spring.
The present methods of hinging suffer from two drawbacks. First, many of the hinge arrangements create lateral loads on the flip cover. For instance, the cam and spring arrangement described above produces a lateral load against the flip cover. Typically, such a lateral load is asymmetrically applied to the flip cover, because one hinge typically is not laterally loaded so as to allow for acoustic coupling. Due the asymmetrical loading, the hinge cover may not fit properly, causing aesthetic dissatisfaction and/or significant stress may be placed on the flip cover, leading to undesirable fatigue and failure. Second, the available hinge mechanisms do not cause the flip cover to automatically assume the open position. That is, the flip covers must be moved into the open position, rather than springing into an open position when released from a catch.
In light of the above, there remains a need for a hinging arrangement that does not produce lateral loading and that causes the flip cover to automatically assume the open position when released. Further, it would be desirable if such a hinging arrangement optionally allowed for acoustic coupling between the flip cover and the device's main body.